Web-spinning fibers and films of benzimidazo-benzophenanthroline polymers

ABSTRACT

PROCESSES ARE PROVIDED FOR PRODUCING SHAPED ARTICLES SUCH AS FIBERS OR FILMS FROM SULFURIC ACID SOLUTIONS OF BENZIMIDAZO-BENZOPHENANTHROLINE POLYMERS BY EXTRUDING THE SOLUTION INTO A COAGULATION MEDIUM WHICH MAY BE DIMETHYFORMAMIDE, DIMETHYLACETAMIDE, N-METHYL-2-PYRROLIDONE, OR MIXTURES THEREOF. TO IMPROVE PHYSICAL PROPERTIES THE COAGULATED ARTICLES MAY BY SUBSEQUENTLY HOT DRAWN.

United States Patent O WEB-SPINNING FIBERS AND FILMS F BENZ-IMlDAZO-BENZOPHENANTHROLINE POLYMERS Michael Dunay, Fanwood, and JamesA. Parker, Plainfield, N.J., assignors to Celanese Corporation, New

York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 21, 1969,Ser. No. 809,367

Int. Cl. D01f 7/04 US. Cl. 264-184 7 Claims ABSTRACT OF THE DISCLOSUREProcesses are provided for producing shaped articles such as fibers orfilms from sulfuric acid solutions of benzimidazo-benzophenanthrolinepolymers by extruding the solution into a coagulation medium which maybe dimethylformamide, dimethylacetamide, N-methyl-Z-pyrrolidone, ormixtures thereof. To improve physical properties the coagulated articlesmay be subsequently hot drawn.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a process for forming shaped articles frombenzimidazo-benzophenanthroline polymers. This invention further relatesto a process for forming filaments, fibers, films, and the like frombis(benzimidazobenzophenanthroline) polymers which hereinafter may bereferred to generally as BBB polymers.

Description of the prior art In recent years, new types of hightemperature resistant polymers, such as the linear polybenzimidazoles(PBI), have attracted attention in connection with the fabrication ofarticles such as re-entry parachutes for space vehicles, hightemperature insulating materials, and the like. As an outgrowth of this,polymers of the benzimidazo-benzophenanthroline type, and particularlythe poly (bisbenzimidazo benzophenanthroline) type (BBB), made asdescribed, for example, in an earlier copending application, Ser. No.657,868, filed Aug. 2, 1967, and assigned to the assignee of the presentapplication, have been found to give particularly useful products inthis connection.

As described in the aforementioned copending application Ser. No.657,868, fibers and other shaped articles of satisfactory properties canbe made from BBB type polymers by solution spinning a dope containingthe BBB polymer dissolved in sulfuric acid solvent into an aqueousdilute sulfuric acid coagulation bath. After such wet spinning, theresulting precursor (as spun) fibers or other shaped articles arenormally washed thoroughly in a dilute alkaline bath in order toneutralize and remove excess sulfuric acid, thereafter washed withwater, and then hot drawn to improve their physical characteristics,e.g., tenacity, elongation, etc.

Disadvantages, however, normally associated with the above described wetspinning process include the necessity of using the alkaline wash bathto neutralize and remove excess sulfuric acid, and the apparentinability of the process to produce high, e.g., 100 or higher, denierfilaments or fibers without incurring unwanted voids in the filament orfiber structure.

The search has continued, therefore, for alternative processes forforming shaped articles from the benzimidazo-benzophenanthrolinepolymers. The present invention was made as a result of that search.

SUMMARY OF THE INVENTION Accordingly, an object of the present inventionis to provide processes for forming shaped articles, such as filamentsand fibers, from benzimidazo-benzophenanthro line polymers.

Another objert of the present invention is to provide a wet spinningprocess for producing shaped articles from sulfuric acid solutions,i.e., dopes, of bisbenzimidazobenzophenanthroline (BBB) polymers, whichprocess avoids or substantially alleviates the disadvantages of suchprocesses heretofore described.

A further object is the provision of a wet spinning process for sulfuricacid solutions of BBB polymers which employs novel coagulating baths inthe system, which process does not require subsequent acid neutralizingbaths, and which can produce high denier BBB fibers that aresubstantially void-free.

Other and further objects of the invention will become apparent from thefollowing more detailed description.

In accordance with the present invention, shaped articles such asfilaments, fibers and films are formed frombenzimidazo-benzophenanthroline polymers by preparing a dope or solutionof the polymer in an acid solvent such as concentrated sulfuric acid,and extruding the acid dope or solution into a coagulation mediumconsisting essentially of an amide which can be dimethylformamide,dimethylacetamide, N-methyl-Z-pyrrolidone, or mixtures thereof.

Preferably, the coagulation medium consists essentially ofdimethylacetamide.

Further, there is normally no need for any subsequent acid neutralizingbath for the amide coagulation medium concurrently neutralizes the acidsolvent.

After the concurrent coagulation and neutralization, the shaped articlessuch as fibers or films can be washed with water to remove any amide,and hot drawn to improve physical properties. The articles obtainedthereby are essentially void-free and may have a denier of or higher.

DESCRIPTION OF PREFERRED EMBODIMENTS The starting polymer The presentinvention is generally applicable to benzimidazo-benzophenanthrolinepolymers, and more preferably, topoly(bisbenzimidazo-benzophanthroline).

As is now otherwise known in the art, these BBB type polymers are madeby mixing and condensing (l) at least one organic tetraamine having thestructural formula wherein R is a monocyclic or bicyclic aromatic orcycloat least one tetracarboxylic acid (which also may be in the form ofa corresponding anhydride) having the structural formula IIOOC COOH RIHOOC COOH wherein R is a tetravalent radical containing at least 2carbon atoms and wherein no more than 2 carboxyl or carbonyl groups ofsaid acid or anhydride are attached to any one carbon atom of saidtetravalent radical.

Preferably, the tetraamine and the tetracarboxylic acid are reacted insubstantially equal molar quantities.

The polymer used herein may have an inherent viscosity of at least .3and, preferably about 1.0 to 5.0, and most preferably about 2.0 to 3.0.

The inherent viscosity as used herein as measured at 25 C. using aconcentration of .4 g. of the polymer in 100 ml. of 97% H 80 Nonlimitingexamples of the tetraamine monomers which may be used individually or inmutual admixture in forming the desired polymer-sare:3,3-diaminobenzidine; bis (3,4-diamino phenyl) methane; 1,2-bis(3,4-diamino phenyl) ethane; 2,2-bis (3,4-diamino phenyl) propane; bis(3,4-diamino phenyl) ether; bis (3,4-diamino phenyl) sulfide; bis(3,4-diamino phenyl) sulfone; 1,2,4,5- tetraamino benzene;2,3,6,7-tetraamino naphthalene; and the corresponding ring hydrogenatedtetraamines.

Nonlirniting examples of the tetracarboxylic acids include:

pyromellitic acid;

2,3,6,7-naphthalene tetracarboxylic acid;

3,3,4,4'-diphenyl tetracarboxylic acid;

1,4,5,8-naphthalene tetracarboxylic acid;

2,2',3,3'-diphenyl tetracarboxylic acid;

2,2-bis(3,4-dicarboxyphenyl) propane acid;

bis (3,4-dicarboxyphenyl) sulfone acid;

3,4,9,10-perylene tetracarboxylic acid;

bis(3,4-dicarboxyphenyl) ether;

ethylene tetracarboxylic acid;

naphthalene 1,2,4,5-tetracarboxylic acid;

decahydronaphthalene-1,4,5,8-tetracarboxylic acid;

4,8-dimethyl-l,2,3,5,6,7-hexahydronaphthalene-l,2,5,6-

tetracarboxylic acid;

2, 6-dichloronaphthalene-1 ,4,5 ,8-tetracarboxylic acid;

2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid;

2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid;

phenanthrene-l,8,9,l-tetracarboxylic acid;

cyclopentane-1,2,3,4-tetracarboxylic acid;

pyrrolidine-2,3,4,5-tetracarboxylic acid;

pyrazine-2,3,5,6-tetracarboxylic acid;

2,2-bis (2,3-dicarboxyphenyl) propane acid;

1,1-bis (2,3-dicarboxyphenyl) ethane acid;

1,1-bis (3,4-dicarboxyphenyl) ethane acid;

bis (2,3-dicarboxyphenyl) methane acid;

bis (3,4-dicarboxyphenyl) methane acid;

bis (3,4-dicarboxyphenyl) sulfone acid;

benzene-1,2,3,4-tetracarboxylic acid;

1,2,3,4-butane tetracarboxylic acid;

thiophene-2,3,4,5-tetracarboxylic acid;

and similar acids, as well as the anhydrides of such acids.

In a preferred embodiment, the present invention is directed to fibersformed from polytbisbenzimidazobenzophenanthroline), i.e., BBB polymers.Such polymers are formed from 1,4,5,8-naphthalene tetracarboxylic acidand 3,3-diamino benzidine according to the following equation:

A preferred method of preparing BBB polymers includes effecting thepolymerization in polyphosphoric acid (PPA) where the reaction accordingto Equation A occurs and can produce a fully cyclized polymer.

Use of polyphosphoric acid as the solvent permits reactions to becarried out over a wide range of temperatures, e.g., C. to 300 C., morepreferably C. to 250 C., and most preferably, 150 C. to 225 C.

The polyphosphoric acid preferably employed has a P 0 equivalent ofabout 82% to 84%, by weight, which is a solution of approximately 5% to20 orthoand pyrophosphoric acids mixed with various polyphosphoricacids, mostly trimers, tetramers, pentamers and hexamers.

The tetraamines and tetracarboxylic acid or corresponding dianhydridemay also be reacted in an organic liquid which is solvent for at leastone of the reactants, and is inert to the reactants, preferably underanhydrous conditions, at a temperature below C., preferably at below 100C.

To cyclize completely the polymer, subsequent high temperature heatingmay be required in the above described reaction or polymerizationprocess.

Both the reaction temperature and the reaction period used significantlyaffects the degree of polymerization. Generally, reaction periods canrange from about 0.5 to 100 hours, typically 10 to 50 hours, at theabove mentioned reaction temperatures. Higher reaction temperatures tendto result in polymer products having higher inherent viscosity thanpolymers produced at lower temperatures in comparable reaction times.

The manner in which the BBB polymer is formed or polymerized is not apart of the present invention. Thus, any method in addition to thosedescribed above may be used by those skilled in the art.

Wet spinning The polymers of the type just described can be formed intofibers and other shaped articles by extruding a solution of the polymerin sulfuric acid through an opening of predetermined shape into acoagulation medium or bath consisting essentially of an amide such asdimethylacetamide, which results in a coagulated material of a desiredcross-section.

BBB solutions or dopes can be prepared by dissolving suificient polymerin sulfuric acid to yield a final solution suitable for spinning orextrusion which contains about 2% to 15%, preferably about 3% to 10%,and most preferably about 4% to 6%, by weight, of polymer based on thetotal weight of the solution.

The sulfuric acid employed should be at least 92 equivalent weightpercent sulfuric acid, and is preferably from 97 to 100 equivalentweight percent sulfuric acid.

Further, the spinning or casting dopes may contain small amounts, e.g.,about .001 to 1% by weight, of various stabilizing additives and thelike.

As stated above, the polymer spinning solution is then extruded into acoagulation bath consisting essentially of an amide such asdimethylacetamide, which is preferred. Other suitable amides includedimethylformamide, N- rnethyl-Z-pyrrolidone, and mixtures thereof.

The coagulation bath may also contain minor amounts e.g., .001 to 10weight percent of well known additives, e.g., other components which areacid acceptors such as aliphatic and aromatic amines, as well as inertspecies, e.g., aliphatic and aromatic hydrocarbons, which would notsubstantially affect the concurrent coagulation and neutralization.

As stated, the coagulation bath also serves to neutralize the acid inthe spun fibers and must therefore be replaced with fresh amide on abatch wise, continuous, or semicontinuous basis as is well known tothose skilled in the art. Preferably, a continuous stream of fresh amideis added to the coagulating bath with a corresponding removal of thespent amide.

The cogulating bath may be adjusted so that bath temperatures andresidence times effect a reasonable speed in the coagulation of theshaped articles. Generally, bath temperatures between about 20 C. andthe boiling point of the amide, and preferably between 25 C. and 100 C.,and residence times of a few seconds to several minutes, e.g.,preferably about seconds to 5 minutes, and more preferably about toseconds, are used.

After such wet spinning, the resulting precursor (as spun) fibers orother shaped articles may be washed with water in order to remove excessamide and neutralized acid.

The water washing medium is usually maintained at a temperature of aboutC. to 90 C., and preferably at about 50 C. to 80 C., and is usuallycontained in a bath through which the shaped articles are passedsubsequent to their passage through the coagulation bath, as in acontinuous process.

To improve physical properties, the fibers or other shaped articles maybe hot drawn at temperatures of at least about 250 C., e.g.,temperatures of about 250 C. to 700 C.

Preferably, the fibers or other shaped articles are hot drawn whilestill wet, e.g., contain from about 50 and up to 500 percent by weightof water, due to the water wash. Surprisingly, this gives the advantageof being able to draw at lower temperatures, e.g., about 250 C. to 350C., and preferably about 260 C. to 280 C., versus the highertemperatures, e.g., 500 C. to 600 C., which may be required whensubstantially dry fibers are hot drawn.

The heat source for the hot drawing may be a heated drawing shoe, aheated rod or pin, a muflle furnace, or the like as is conventionallyused and well known in the art.

The shaped articles may be hot drawn at draw ratios of about 1.1 toabout 3.0, and preferably between about 1.2 and about 1.5. The term drawratio" as used herein has the conventional meaning as used in the artand is the ratio of the peripheral speed, in units of length per unittime, of the wind-up or take-up roll to that of the feed or deliveryroll in the drawiig system.

The present invention is further illustrated by the following exampleswhich produce strong and void-free BBB fibers. All parts and percentagesin the examples, as well as in the specification and claims, are byweight unless otherwise indicated.

EXAMPLE I The BBB polymer used is a condensation product ofl,4,5,8-naphthalene tetracarboxylic acid and 3,3'-diaminobenzidinehaving an inherent viscosity of about 2.6. For use in the illustrativeoperation, this polymer is dissolved in 97% sulfuric acid to form aspinning solution containing about 5% dissolved polymer andcharacterized by a solution viscosity of 2100 poises at 60 C.

This solution is charged into a reservoir from whence it is extrudedunder 65 p.s.i.g. pressure through a conventional spinneret immersed ina coagulation bath, spinning at a rate of about 2 m./min.

The spinneret is a one-fil, ZOO-micron jet,i.e., a spinneret having anorifice of ZOO-micron diameter, though other spinnerets may, of course,be used similarly.

The coagulation bath used is 100% dimethylacetamide, and is at atemperature of about 25 C., with a fiber residence time in thecoagulation bath of about 15 seconds.

The resulting wet spun fibers pass from the coagulation bath to a waterwash which is maintained at a temperature of about C. with a residencetime of about 5 seconds in the wash bath.

From the wash bath the washed fibers while still wet pass over a heateddrawing shoe maintained at a temperature of 270 C., with a shoeresidence time of about 2 seconds. A draw ratio of about 1.5 ismaintained.

The resulting BBB fibers are of good quality, i.e., are strong andvoid-free.

EXAMPLE II Example I is repeated with the exception that a coagulationbath of dimethylforma-rnide is substituted for the coagulation bath ofdimethylacetamide to produce BBB fibers of good quality.

EXAMPLE II-I Example I is repeated with the exception that a coagulationbath of N methyl 2 pyrrolidone is substituted for the coagulation bathof dimethylacetamide to produce BBB fibers of good quality.

While the invention has been described in preferred embodiments,variations and changes may be made therein without departing from thespirit of the invention.

We claim:

1. An improved process for forming fibers or films of benzimidazobenzophenanthroline polymer which process comprises (a) forming an acidspinning dope containing between about 2% and 15% of the polymerdissolved in sulfuric acid solvent having an H 80 content of at leastabout 92%,

(b) extruding the resulting dope into a coagulation medium consistingessentially of an amide selected from the group consisting ofdimethylformamide, dimethylacetamide, N methyl 2 pyrrolidone, andmixtures thereof maintained at a temperature between about 25 C. and C.,and thereafter,

(c) recovering the coagulated material.

2. A process according to claim 1 wherein the coagulation mediumconsists essentially of dimethylacetamide.

3. A process according to claim 1 which further comprises (i) washingthe resulting coagulated material with water,

(ii) drawing the washed material at a temperature above about 250 C. andthereafter (iii) recovering the drawn material.

4. An improved process for forming fibers or films from an acid dopecontaining bis(benzimidazo-benzophenanthroline) polymer dissolved insulfuric acid solvent having an H 50 content of at least 92%, the dopecomprising between about 3% and 10% dissolved polymer, which processcomprises (a) extruding the dope through an orifice into a coagulationmedium consisting essentially of an amide selected from the groupconsisting of dimethylformamide, dimethylacetamide, and N methyl 2pyrrolidone, at a temperature between about 25 C. and 100 C.,

(b) washing the resulting coagulated material with water,

(c) drawing the washed material at a draw ratio between about 1.1 and3.0, and thereafter (d) recovering the resulting material.

5. A process according to claim 4 wherein the drawing is done at a drawratio between about 1.2 and about $50 and at a temperature between about250 C. and

6. A process according to claim 5 wherein the bath consists essentiallyof dimethylacetamide and is at a temperature between about 250 C. and 70C.

7. An improved process for forming fibers ofbis(benzimidazo-benzophenanthroline) polymer, which process compnses,

(a) forming a dope of the polymer in sulfuric acid solvent having an H80 content of at least 97%, the

7 resulting dope comprising between about 4% to 6% OTHER REFERENCESdissolved polym r, Gloor: Fiber Formation and Drawing of Poly (bis- (b)sp1nn1ng the resulting dope into a coagulation rnebenzimidazobenzophenanthroline),, from Fiber Spin diurn consisting essentially ofdimethylacetamide at nin and Drawin o 0 g g, edlted by Coplan,lntersclence Puba temperature between about 25 C. and 70 C., 5 ushers,1967 151463.

(c) washing the resulting coagulated fibers with Water, t yrnposlumFocuses on Heat-Res1stantF1be1s, Chemi- (d) drawlng the Washed fibersWhile still Wet, at a draw ratio between about 1.1 and about 3.0 and ata temcal & Engmeenng News Sapt' 1968 40 perature between about 250 C.and 350 C., and JULIUS FROME Primary Examiner (e) thereafter recoveringthe resulting drawn fibers. 1O

H. MINTZ, Asslstant Examiner References Cited UNITED STATES PATENTS3,414,543 12/1968 Paufler 260-47 r 3,441,640 4/1969 Santangelo 264203 19US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5 ,30 Dated February 9, 1971 Inventor) Michael Dunay and James A. Parker Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In column 2 line 10, delctebb jert" and insert "object In column 5, line49 delete "drawiig" and insert drz-lwln In column 0, line 70 delete 250C. anti insert. 1" "(3.

Signed and sealed this 22nd day of June 1 971 (SEAL) Attest:

EDWARD M.FI.|ETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents

